Impact welding



Dec. 15, 1942. R. s. THACKER 2,305,042

IMPACT WELDING- Filed May 28, 1940 4 Sheets-Sheet l Tiff +V P//y j.' @daf/er ATTORNEY Dec. 1 5, 1942.

f4 za f5 R. S. THACKER IMPACT WELDING Filed May 28, 194C 4 Sheets-Sheet 2 Q INVEN TOR,

DBC. 15, 1942. R, s, THACKER 2,305,042

IMPACT WELDING Filed May 28, 1940 4 Sheets-Sheet 5 AT TOR N EY Dec. l5, 1942. v R, s' THACKER 2,305,042

IMPACT WELDING Patented Dec.`15. 1942 IMPACT WELDING Ralph S. Thacker, West Los Angeles, Calif., as-

signor to Leo M. Harvey, La Canada, Calif.

Application May 28, 1940, Serial No. 337,638

(Cl. 21S-J0) 5 claims.

This `invention relates to the art of welding,.

and particularly to one in which the parts to be welded together are subjected to a forging pressure.

In general the art of joining two metals together while they are heated to a plastic condition by forging or hammering is old; but vthe equipment required for this old process is cumbersome and heavy, and the operation is necessarily slow.

It is one of the objects of this invention to make I it possible rapidly to produce such welds with simple apparatus, either stationary or portable, and without the exercise of any uncommon degree of skill.

It is another object of this invention to make it possible to utilize electrical energy for heating those portions of the pieces of metal which are to be welded together; and particularly by the passage of current between the pieces.

In order to attain these objects, a particular cycle of operations is provided, which is initiated at will by the operator, and which can be repeated in rapid succession as often as required. This cycle includes the step of ilrst applying a moderate pressure between the pieces to be welded, so as to ensure continuity in the path for the heating current to be passed through the contacting surfaces, and of such order that the current encounters suilicient resistance rapidly to cause the pieces in the vicinity of the pressure application to become plastic or molten.

After this pressure is attained, the pieces are heated by the passage of an electric heating current, and simultaneously the pressure is increased. This -causes more intimate contact bein the weld area immediately after the plastic area is congealed;

This invention possesses many other advantages, and has other objects which may be made more easily apparent from a consideration ofseveral embodiments of the invention. For this purpose there are shown a few forms in the drawings accompanying and forming part of the present specification. These forms will now be described in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description isnot to be taken in a limiting sense, since the scope of the Invention is best defined by the appended claims.

Referring to the drawings: Figure 1 is a schematic diagram to aid in explaining the invention;

Fig. 2 is a graph illustrating the various steps of the welding process;

Fig. 3 is a viewl mainly in section, of one form of apparatus adapted to be utilized for practicing the invention; y

Fig. 4 is a schematic diagram of the apparatus illustrated in Fig. 3;

Fig. 5 is a view similar to Fig.. 3 of a modied form of the apparatus; and

Fig. 6 is an enlarged fragmentary section oi a portion ofthe apparatus illustrated in-Fig. 3. The two pieces to be joined by impact welding in accordance with the invention are illustrated as flat plates I and 2 (Figs. 1 and 3). 'I'hese plates may be of weldable metal, such as steel or iron. In order to obtain a weld, an electrode structure 3 is arranged to be pressed against the piece I for conducting a heating current through the contacting surfaces of pieces I and 2. 'I'he current and resistance which is determined by pressure are of such values to produce sufiicient heat to cause a pool I of molten or plastic metal to form. This pool is intersected at the contacting surfaces 5. In Fig. 1, a source 6 of low potential heating current is indicated, connected to the electrode structure 3 and to the lower plate 2.

'Ihe heating of the metal in this manner is secured by appropriate pressure applied between the pieces I and 2 by the structure 3. .This pressure is such that during the interval that the a heating current flows, sumcient resistance exists between the pieces I and 2. I

In the cycle employed in this invention, the pressure applied by electrode 3 is gradually increased to a maximum and then released. The current flow is maintained only for an intermediate portion of the period during which pressure is applied. The pressure gradually builds up so as to produce proper admixture of the plastic metal forming pool 4, and is applied with con.. tinually greater force even after the current is stopped. This results in an impact weld, for as the pool 4 cools. the pressure ensures intimate union of the pieces I and 2 by the aid of the coalesced metal that forms the plastic pool I.

Furthermore, if desired, at the conclusion of the pressure increasing cycle, a hammer blow may be exerted upon the electrode 3 for further intensive working of the metal to produce the desired grain structure in the weld.

This system of welding is indicated graphically in Fig. 2, where the abscissae of the graph represent time; and the ordinates represent pressure as applied between the plates I and 2. During the first period, the pressure builds up continuously from a low value to a point corresponding to the ordinate of point 1. At this point the heating current is applied. This heating current is continued until the point 8 is reached. At the same time the pressure is continuously increased, corresponding to the ordinate of the point 3. Thereafter, at the conclusion of the application of the heating current, there is a holding pressure which continuously increases to a value corresponding to the ordinate of point 3. During the application of this holding pressure the meta'l of pool 4 congeals. At the conclusion of the gradual increase of pressure, a violent hammer blow may be struck, corresponding to a pressure represented by the ordinate of point III. Immediately after the hammer blow is delivered, the pressure drops to zero.

The time consumed by the entire cycle, as represented by the abscissa of point Il or point 9 may be very short, of the order of a fraction of a second.

The apparatus whereby this cycle may be accomplished is illustrated somewhat diagrammatically in Figs. 3, 4 and 6.

The electrode structure 3 in this instance is shown as carried by a member II of cylindrical form, guided for axial movement in an aperture I2. This aperture I2 is located in the hub I3 of a cover member I4.

Provisions are made for exerting a gradually increasing pressure upon the member II for' transmission of that pressure to the electrode structure 3. For this purpose use is made of a compression spring I6 housed in a barrel I 1. 'Ihe cover member I4 has a flange telescoping within the right hand end of the barrel II, and thus serves as a cap or cover for the right hand end of barrel I1. The barrel I1 and the cover member I4 may be appropriately joined together.

One end of the compression spring I3 is seated on the nange I5, shown in this instance as formed integrally with the member II. The left hand end ofthe spring I6 abuts a ange I8 formed on an axially movable hollow sleeve I3. This sleeve Il is located within the barrel I1, and may be coaxial therewith. It is arranged to be driven toward the right for compressing the spring I6, and thereby increasing the pressure acting upon the member II.

For causing motion of the sleeve I3, use is made of a cylinder and piston mechanism adapted to operate for example by the aid of compressed air. Thus for example there is a stationary cylunder the iniiuence of expanding compressed air, is arranged to strike the end 25 of an impact sustaining member 26. This impact sustaining member 26 is guided for free sliding movement in the right hand end of the cylinder 20. It is ljoined as by the aid of its end flange 21 to the right hand end. of the sleeve I9. This joining may be accomplished for example by an annular welded bead 28.

Movement ot the piston 24 toward the right ultimately causes engagement of the piston with the left hand surface of the extension 25; and thereafter the sleeve I9 is carried toward the right, causing compression of the spring I6 and a driving force upon the electrode 3.

The arrangement is furthermore such that if desired, a violent hammer blow may be exerted upon the structure carrying the electrode 3 at the completion of the piston stroke. Thus for example the member I I may carry an anvil member 29. This anvil 29 may be attached to the left hand end of member II as bythe aid of the threaded extension 30. The anvil 29 is purposely made easily detachable from member II, so that different anvils of varying lengths may be substituted. In this way that point during the cycle of travel of the piston 24 when the hammer blow is delivered, can be determined.

As heretofore stated, the gradually increasing pressure upon the electrode 3. is so arranged that at some intermediate interval of the operative movement of the piston 24 an electric current can be passed through pieces I Aand 2 for heating the area to be welded. The period of heating begins a short time after the spring I6 is beginning to compress, and the heating effect i made to last for almost the end of the pressure exertion cycle. As the pressure is increased, there is a corresponding variation in current flow; and since resistance is greatest between the interfaces of pieces I and 2, the heating effect is quite well confined to the place where these two pieces are in contact, and under the pressure exerted by the electrode 3.

There is diagrammatically illustrated in Fig. 3 one manner in which the control of the electric heating circuit may be eil'ected. For example, a

, bar or rod 3I may extend between the cover I4 inder 23 reaching nearly to the right hand end of the sleeve I3. This cylinder 2|I has an integral iiange 2l over which telescopes the right hand end of the barrel II and to which the barrel I'I may be fastened.l Thecylinder 2|I may be also provided with an internally threaded integral collar 22 for the accommodation of a body member 23 which incorporates the control apparatus, such as valves and theirbperating mechanism. For the present it is sufilcient to note that the cylinder 2l is so arranged that it' to ilange 2|. This bar or sleeve 32 attached to the flange I5 of mem-ber II. Similarly the flange I3 ot the tubular member I3 carries a conducting sleeve 33. The sleeve 32 carries a. spring contact finger 34. This contact nger ls insulated from the sleeve 32 and is in the path ofmovement of the conducting sleeve 33. Movement of the sleeve I9 toward the right to compress 'spring I6 causes movement of the conducting member 33 toward the right and ultimately contact is made with the spring linger 34. When this occurs, a control cricuit is completed through the grounded conectlon 33, connection 43, contact linger 34 and sleeve 33, for causing a time delay switch 35 to close. When this occurs, the main heating circuit is completed from rod passes through a .h mains 31 and 38 through the switch 35, terminal narily, as explained in connection with the graph of Fig. 2, this heating circuit is applied to near the end oi' the stroke of the piston 24.

Byappropriate choice of a source of electrical energy, the interval of heating through the elec- The control mechanism for the piston 24 in cylinder 26 is illustrated somewhat diagrammatically in Figs. 3 and 6, and it is' shown in still more diagrammatic form in Fig. 4.

The body 23 is provided at one end with an annular port 4| communicating with the left hand or open end'of the cylinder 26. This port 4| is in communication, as by the aid of aperture 42, with an inlet chamber 43. The aperture 42 extends through a wall 44 formed adjacent the right hand portion of the body 23, for the accommodation of various passages or ports for purposes hereinafter to be described.

The inlet space 43 is dened by wall 45 forming a ilat valve seat 46. In the inactive or quiescent position, this inlet space 43 is closed against the entryof air under pressure, by an appropriate valve closure structure.

The closure member for the valve seat 46 is shown in this instance as a yielding disk 41, having its edge in contact with the seat 46. The closure member 41 is mounted in any appropriate manner upon the end of a movable valve operating piston member 46. This piston member is slidable in appropriate guiding cylinder walls 46 formed in the body 23. In the inactive position, air under pressure is conducted to the lower. side of the piston structure 48 to keep the valve closure 41 seated. However, -by appropriate mechanism this piston 48 may be moved down-l tive through space 43, aperture 42 and port 4|,

to urge the piston 24 toward the right, and thereby to convert the potential energy. into kinetic energy of the moving piston 24.

The reservoir 56 is shown in this instance as being deiined by a wall 5| and by a guiding hub 86 extending axially to the piston 24.

'I'he passage of air into the space 56 and into I the lower side of the piston 48 which carries the closure member 41, is eiected through a valve port 52. This valve port may be formed within a valve member 53 threaded in a wall 54 integral with the -body member 23. In the inactive position this valve port 5 2 is opened but may be closed by a vaive'closure 55.

Air under pressure is lead to a space 56 formed in body 23, and leading to the right hand side of the port 52, as by the aid of a conduit 51. This conduit 51 may be connected, as by flexible hose, to any appropriate source of air pressure, such as an air compressor system or tank. The air passes from space 56 through port 52 and into a space 56. From this space there are two paths in parallel for the air; one path is by way of the connection 56 to a pressure reducer valve 66. From the pressure reducer valve there is a connection 6| leading directly to the reservoir 56.

The air in reservoir 56 is thus kept at a desired pressure prior to the opening of the valve closure 41. I

Air is also4 permitted to pass from space 56 to a passage 62 formed in the wall of member 23, as well as in thewall 44. This passageway conducts air to the space 63 beneath the piston 48.

In order that this space be maintained closed. a cover member 64 is provided, attached to the body 23.

By simultaneous manipulation of valve 55 and piston 48, the flow ci air as just described can be interrupted, and the reservoir 56 can be opened. To open the reservoir, the space 63 is exhausted, and .the valve closure 41 then moved to open position. Thereupon the piston 24 is' urged by air pressure inwardlyof the cylinder 26. A diagrammatic representation of mechanism to accomplish this result includes a manually operated lever 65. This lever is shown as pivoted near the upper end of a handle 65 attached to the cover member 61 for the left hand end of the body 23. Movement of the lever 65 in a counterclockwise direction causes substantially simultaneous opening of the valve closure 41 and closing of the valve port 52. For this purpose the valve 55 may be provided with a stem 68 projecting through the cover 61. appropriately arranged to slide through a suitable packing giand structure 69. Its left hand end may terminate in an enlarged head 16 adapted to be contacted by an actuator 1|. This actuator 1| is pivotally mounted intermediate the lever 65. A coil spring 12 may if desired be interposed between the cover 61 and the head 16 for normally urging the valve stem 68 toward open position. The actuator 1I is caused to depress the stem 66 and closes the valvev 52l Simultaneously the lower end of lever 65 engages one arm of a bell crank lever 13. This bell crank lever may be appropriately pivoted on the body 23. The short arm 14 of the lever 13 is arranged to push a push rod 15 projecting through thecover 64. 9

For this purpose the push rod 15 may be appropriately guided and sealed against escape of air, in cover 64. The innerv end of the push rod 15 is arranged to break a toggle mechanism connected between the cover 64 and the piston 46. This toggle mechanism includes a clevis 16 which also serves to hold the closure disk 41 in place on the piston 48. The toggle also includes a clevis 11 attached to the cover 64. The integral stud 18 attached to the clevis 11 passes through the cover 64 and may serve asa fasten- 'ing means for the clevis, as by the aid of the nut 19. A threaded cap 66 may be provided for covering the projecting stud 18. v

Joining the clevises 16 and 11 are a pair of toggle links 8| and 82. Normally the air pressure in chamber 63 serves to hold the toggle mechanism in substantially the straight position illustrated in Fig. 3. A tension spring 83 may be utilized to assist in urging the toggle mechanism to this position. However, when the bell crank lever 13 is rotated in a counterclockwise direction the push rod 15 operates on link 62 and breaks the toggle, depressing the closure disk 41 to open position. The pressure of the air escaping from the reservoir 56 past the disk v41 keeps the valve open until the completionof the welding cycle.

. In order to ensure that air can exhaust from the space 63 so that there may be no interference with the opening of the valve closure, an ex- This stem 68 may be haust passage 84 is provided, leading from the space 83. This exhaust passage leads into a space 85, connected to atmosphere. This space 85 is formed between the walls 5| and 54. It is controlled by an exhaust valve closure 81 cooperating with a valve port forming member 88 in wall 54. The stem 89 for closure 81 is guided through the cover member 81 in the same manner as stem 88 for valve 52. It is likewise adapted to be depressed by the actuator 1I upon movement toward the right of the control lever 85. Accordingly when control lever 85 is moved in a counterclockwise direction, the exhaust valve 81 opens, and air from space 63 is exhausted through the exhaust passage 90.

Upon release of the lever 85, the valve stem springs such as spring 12, operate on actuator 1I to return the mechanism to the position shown in Fig. 3. In this position air can again4 enter into the reservoir 50 past valve 52, and through the regulator valve 80. Air can also pass through passageway 62 to the lower side of the piston 48, urging the closure 41 to its closed position, and straightening the toggle mechanism.

As thus far described, the piston 24 at the conclusion of the cycle might be retained in its extreme right hand position in cylinder 20. Provisions are made, however, for 'returning the piston 24 to the starting position illustrated, upon release of lever 85. For this purpose, automatic mechanism is provided operating by air pressure, to move the piston 24 toward the left.

The mechanism for accomplishing this pur- I pose includes a stem 9| which projects through a cylinder sleeve 92 fastened inside of the hub 88. This stem 9| is detachably connected to the piston 24. For this purpose the piston 24 has an axial aperture 93 in which the rounded end of the stem 9| may project. The stem 9| furthermore has'a groove 94 formed by slanting walls and adapted to cooperate with a plurality of spring pressed balls 95. 'I'hese balls 95 are guided in appropriate radial apertures in the piston 24, and are urged inwardly into groove 94 for detachably connecting the stem 9| to piston 29.

A This is accomplished by the aid of springs 95. These springs are held in compressed position by the headless screws 91 threaded into the outer portions of end radial apertures.

Upon release oi air from reservoir 50 through the p'ort 4| to move the piston 24 toward the right, this piston 24 moves sulciently violently so as to release the balls 95 and piston 24 is free to travel without restraint in the cylinder 20.

However, the stem 9| is guided for axial movement and is intended to follow the piston 24 and to be urged into engagement with the piston. For this purpose the stem 9| is shown as guided through a packing gland structure 98 in a boss 99 formed concentrically with the hub 88. At its left hand end the stem 9| carries an auxiliary piston structure |00 adapted to slide within the cylinder 92. The piston |00 is adapted to be urged toward the right to follow the piston 24 by air pressure in space |0| Compressed air can enter space |0| past a valve closure |02 of similar construction to the valves already described. This valve closure |02 operates against a seat formed in valve member |08 .and is normally closed in the inactive position. However, when the actuator 1| depresses the stem |04 of closure |02, compressed air is free to pass into space |0I, and the piston 00 moves toward the right. This occurs substantially simultaneously with the closing of valve closure 52 and the opening of the valve closure". Accordingly, the stem 9| is urged downwardly by air pressure to be re-engaged by the balls 95. The right hand end of the stem 9| is rounded in order to ensure that it can act as a cam to spread the balls 95. Furthermore, the aperture 92 in piston 24 has a ilared portion ||4 to assist in guiding the rounded end of stein 9| into the aperture.

Upon completion or the welding operation, the actuator 1| may be released. This causes the entry of air within the cylinder 92 in the space to the right of the piston |00 tomove the piston |00 to the extreme left hand position indicated. For this purpose the cylinder 92 has one or more openings |05 communicating with the air passage 82. Accordingly when passage 82 is again connected to the inlet conduit 51, past the closure 55. the piston |00 and its stem 9| are urged toward the left, and the main piston 24 is carried along with the stem 9|.

Exhaust passages are also provided for exhausting the space from one or the other side of the auxiliary piston |00. Thus in the inactive position shown in Fig. 3, the space |0| is shown as vented past the exhaust valve closure |08 which is open when the apparatus is inactive. This valve closure cooperates with valve structure |01, and is urged to its seat when the lever 85 is moved to initiate the welding cycle. Since valve closure |02 simultaneously opens, air pressure is then e'ective to urge the auxiliary piston |00 toward the right.

Similarly, when the lever 85 is moved to initiate the welding cycle, the exhaust valve closure 81 is opened, and this serves simultaneously to exhaust air from the right hand side of the auxiliary piston 00, permitting free movement of this piston. This is effective through the ports |05, and passage 82. As soon as lever 85 is released, the exhaust valve |01 opens, and exhaust valve 81 is closed; and at the same time, compressed air passes into cylinder 92 to move the piston |00 toward the left.

Provisions may also be made to ensure that the air in cylinder 20 on the left hand side of the piston 24 will be exhausted when the lever 85 is released at the conclusion of the welding cycle, thereby removing any resistance to the return of the piston. For this purpose, as illustrated diagrammatically in Fig. 4, there is provided a passageway |09 leading from the space 48 to the exhaust valve |01. This passageway may be controlled by a ball check valve diagrammatically illustrated at |09, which permits passage of air only outwardly from. the space 43. Y

The operation of the welding mechanism may now be summarized. In the position indicated in Fig. 3, the reservoir 50 is iilled with air and is kept sealed against escape past the valve closure 41. Furthermore, air pressure is eilective against the right hand side of the auxiliary piston |00, holding the main piston 24 in its inactive position.

Upon depressing the lever 85, the valve closure 41 is depressed to the open position by the aid of push rod 15 operating on the toggle mechanism. At the same time air is exhausted from the space 88 and air is permitted to enter the space |0I. Accordingly air is effective immediately to urge the piston 24 by compressed air passing through port 4|, to cause piston 24 to strike the extension 25. Thereafter the kinetic energy of the piston 24, imparted to it by the expanding air from reservoir 50, is converted into the work o1' compressing spring I8. The auxiliary piston I0| and stem 9| follow this movement.

IBS is also urged to closed position.' and valve increasing the pressure betweenthe two elements closure |02 is urged to open position, supplying air to the left hand side of the auxiliary piston |00.

Upon release of the lever 65, the valve closure 41 is returned to the position illustrated in Figs. 3, 4 and 6. 'Ihe reservoir 50 promptly becomes iilled with compressed air at the desired pressure, and the auxiliary piston |00 is moved toward the left to returnmain piston 24 to the inactive position indicated. Air is also passed into space 63 to cause valve closure 41 to seal the. reservoir 5I).

In the travel of .the piston 24, the extension 25 is engaged and the spring I6 is gradually compressed. At the conclusion of the stroke the anvil 29 may be struck, if desired, to complete the welding operation by forging. At an intermediate point, the circuit for control of the time delay switch 35 is completed and heating current is permitted to pass for a short interval.

It is not essential that the motive power be compressed air. It is feasible instead to provide an electromagnet coil I I0 (Fig. 5) for operating upon the magnetic piston III to effect the same result. A similar structure may be used to retract the piston. In this instance the handle I I2 of the device may be provided with a switch for controlling the current -to the coil III), as by the aid of an operating member IIS. In other respects the apparatus may be similar to that described, switches in general being utilized in place of valves.

What I claim is:

1. The process of electrically welding contacting metallic elements together, which comprises increasing the pressure between the two elements in a continuous manner between a low value and a high value, and passing an electric current between the elements for an interval beginning substantially above the low pressure and ending substantially below the high pressure, said current producing a yelding temperature at the locality of the contact.

2. The process of electrically welding contacting metallic elements together, which comprises in a continuous manner between a low value and a high value, passing an electric current between the elements for an interval beginning substantially above the low pressure and ending substantially below the high pressure, said current producing a welding temperature a't the locality of the contact, and suddenly increasing the pressure beyond said high value.

3. The process of electrically welding contacting metallic elements together, which comprises pressing an electrode against one of the elements to urge the .elements toward each other, increas-V ing -thepressure on the electrode in a continuous manner, so that the pressureincreases continuously between a low and a high value, and passing an electric current through said electrode and said elements for an interval beginning substantially above the initial pressure and endingsubstantially below the high pressure, said current producing a welding temperature at the locality of the contact.

4. The process of electrically welding'contacting metallic elements together, which comprises pressing an electrode against one of the elements to urge the elements toward each other, increasing the pressure on the electrode in a continuous manner, so that the pressure increases continuously between a, low and a high value, passing an electric current through said electrode and said elements for an interval beginning substantially above the initial pressure and endingsubstantially below the high pressure, said current producing a welding temperature at the locality of the contact, and suddenly'increasing the pressure beyond said high value.

5. The process of electrically welding contacting metallic elements` together, which comprises expending a limited amount of mechanical energy upon a resilient medium that transmits a pressure upon the elements, in such manner as continuously to increase the pressure thus transmitted, to an upper linut and passing an electric current for an interval beginning at an instant when the pressure is substantially above the beginning pressure, and ending at an instant when the pressure is substantially below the upper limit, said current producing a welding temperature at the locality of the contact.

RALPH S. THACKER. 

